Maltose, also known as malt sugar, is a disaccharide composed of two glucose molecules linked by a specific glycosidic bond. It is a reducing sugar widely occurring in nature as a product of starch breakdown. Maltose plays an important role in carbohydrate metabolism and has applications in food and fermentation industries.
Chemical Structure
Maltose consists of two alpha-D-glucose units connected by an α(1→4) glycosidic bond. This bond forms through a condensation reaction during which a water molecule is released. Its chemical formula is C₁₂H₂₂O₁₁, with a molar mass of approximately 342.3 g/mol. One glucose unit retains a free anomeric carbon, giving maltose its reducing properties. Due to this free aldehyde group in solution, maltose undergoes mutarotation and exists as a mixture of α- and β-anomers.
Physical and Chemical Properties
Maltose appears as a white, odorless crystalline powder that is soluble in water and moderately sweet—about 30% to 60% as sweet as sucrose. Its melting point ranges from 102 to 165 °C depending on hydration state, and its density is approximately 1.54 g/cm³. Because it is a reducing sugar, maltose produces positive reactions with Benedict’s and Tollens’ reagents.
Upon hydrolysis—catalyzed by the enzyme maltase or by acid treatment—maltose yields two glucose molecules:
Maltose + H₂O →(maltase / hydrolysis)→ 2 glucose
Maltose also reacts with strong acids, generating carbon dioxide, water, and sulfur dioxide.
Biological Role and Production
Maltose is naturally produced during starch digestion when β-amylase cleaves starch by releasing two-glucose fragments. It is found in germinating grains and functions as an intermediate in carbohydrate metabolism. In lean dough, maltose is often the main sugar consumed by yeast during fermentation, contributing to bread making and alcoholic fermentation.
Maltose is a reducing disaccharide composed of two α-D-glucose molecules linked by an α(1→4) glycosidic bond. With distinct physicochemical properties, a key role in carbohydrate metabolism, and significant industrial applications, maltose remains an important molecule in biochemistry, nutrition, and food science.
